This project aims to elucidate the mechanisms involved in transformation of chromatin during formation of spermatozoa in spermatogenesis are during dispersion of sperm nuclei in fertilization in order to obtain further understanding of reproductive processes in mammals and is divided into two major parts: 1. The replacement of somatic type histones by sperm histone during transformation of spermatid chromatin in spermiogenesis will be investigated with special focus on activation and/or mobilization of the chromatin-associated serine-protease. 2. The process of dispersion of sperm chromatin during male pronucleus formation will be studied in relation to proteolytic removal of sperm histone by a special class of acrosin.